I can tell you Spain's data is wrong. The employer's Social Security "contribution" (paid by the worker in the form of lower net wages) exceeds 30% in all cases, plus 6.x% taken from the individual's paycheck ("employee's contribution", as if the other portion didn't come from the employee's salary all the same). The average effective income tax is around 25%. So the reality is way worse than this, without even going into the details of consumption taxes, "especial taxes" (gas, electricity, water, tobacco, etc), property taxes, taxes against savings and wealth, death taxes, taxes on gifts, capital gains taxes... and taxes on top of money that's taxed several times for different "reasons". My estimation is that anyone living off a wage in Spain doesn't really enjoy more than 20% of their "salary".

And then there's the consequence of all this: if you make 10, and I take 8, it's not only that you're "80% my slave"... because by leaving you only with 2, I'm also taking away from your any sort of freedom you have over those 2, because you simply can't live the way you would with the full 10 having 2 only.

So, to answer the question: it's slavery all the same as long as the % taken is bigger than ZERO.